Medications traditionally have been administered in various ways, including orally, subcutaneously, intramuscularly, or intravenously. Other drug delivery systems include transdermal patches, membrane-encased cells genetically engineered to secrete a desired drug (e.g., nerve growth factor or insulin), and slow-release drug systems. Traditional routes of administration require patients to actively follow dosing instructions, for example, when medication is administered orally, such as an antibiotic, hormone, or vitamin, or when repeated visits to the doctor are necessary because the route of administration is by injection. These methods of administration are especially problematic in cases where the patient is a child, elderly, or where the medication must be administered on a chronic basis. Generally, compliance with taking medication is a problem for many adults as they simply forget to take it as recommended or required.
Transdermal patches are used currently to administer drugs such as hormones, estrogen, nicotine, and nitroglycerin (for angina or chest pain). While such a system has been shown to be effective in certain instances, a drug must penetrate the skin barrier in order to be administered via a transdermal patch. Many drugs cannot be administered in effective amounts transdermally. Other slow-release delivery systems are useful, but they require the removal of the matrix itself after the drug has been completely absorbed. Hence, surgery is required to insert the composition and to remove the exhausted matrix from the patient.
Since the sustained release of biological agents was established several decades ago, the sustained release has been advanced by controlling the diffusion of drugs through polymeric matrices and/or the degradation of these polymers. Recently, drug release in proportion to internal or external stimuli has become recognized, which can be achieved by using stimuli-responsive polymeric materials. Many of these polymers achieve their functions by changes in temperature, pH, glucose concentration, and the release of ribosomal enzymes. Biodegradable polymers have great potential for applications as implantable carriers for drug delivery systems. With an auto-feed-back drug delivery system, several physiological changes in a living body can be utilized as the signal inducing polymer degradation and subsequent drug release.
The sustained delivery of antibiotic pharmaceutical agents is often desirable for the treatment of intractable fungal and bacterial infections. Methods of slow drug release have considerable pharmacodynamic advantages over long-term intravenous drug therapy. The former may result in shorter hospitalizations and greater degrees of compliance, and may eliminate the need for indwelling catheters. Slow drug release is usually achieved either by incorporation of a therapeutic drug into an implantable reservoir or by implantation of biodegradable materials containing the desired drug. The development of biodegradable antimicrobial compounds is particularly appealing for the treatment of postsurgical infections and of focal infections in immuno-compromised patients. Efficacies of slow drug release systems are usually determined by measurement of concentrations of the implanted drug in plasma or by assessment of the underlying disease treated (e.g., improving infection or decrease in the size of cancer, etc.).
For chronic heart problems, slow drug release with therapeutic factors having angiogenic, myogenic, and antiarrhythmic potential is very important. The local drug release avoids using larger concentrations or doses to avoid systemic effects. The disclosure of the present application introduces devices, systems, and methods by which implants (biological, chemical or electrical) can be delivered to a tissue and/or organ to provide long term therapeutics.